1. Field of the Invention
The present invention relates to a photoelectric beam system, and, more particularly, to an alignment apparatus for a photoelectric beam system.
2. Description of the Related Art.
Photoelectric beam emitters and their sensors are used for measurement and control operations in which the photoelectric beams are broken or restored between the emitters and the sensors. The photoelectric beam arrangement may be used for counting items along a conveyor belt, measuring the size of objects, detecting the position of a machine part, and many other applications.
One type of photoelectric beam arrangement includes an emitter and a receiver in the same housing. Two separate housings, each including an emitter and a receiver, are positioned on opposite sides of an object's path. The photoelectric beam is transmitted from the emitter to the detector across the path.
In these photoelectric systems, accurate alignment of the housings and, consequently, the optical path must be achieved for proper operation. It is important that the optical system be properly aligned in order to maximize the signal-to-noise ratio. If the system has a poor signal-to-noise ratio, then the system may be susceptible to false alarms caused by environmental conditions such as rain, fog, snow and frost.
One of the problems associated with current alignment methods is that it requires two people to align the photoelectric beams. Known photobeam assemblies incorporate vertical and horizontal alignment controls. The controls are adjusted manually by the installer using a screw adjustment. A signal level output is usually provided for connection to a hand held voltmeter. Adjustments are made to obtain the largest signal levels possible. The signal level measurements are provided at only the receive end of the system. Optimizing the alignment of the transmitter requires a second person. The transmitter and receiver may be 300 feet apart, and thus, even with two people, they may still be difficult to align.
Another problem is that the mounting surface on which the housings are mounted can shift over time, thereby causing a misalignment. In this case, two people must return to the scene in order to correct the misalignment.
What is neither disclosed nor suggested in the prior art is a method of aligning an optical beam that does not require two people, and that involves transmitting two different photobeams in opposite directions between a master unit and a slave unit, adjusting the position of the master unit to align it with the beam from the slave unit, and then adjusting the position of the slave unit to align it with the beam from the master unit.